Mineral oil composition



Patented Nov. 5, 1946 MINERAL OIL COMPOSITION John J. Giammaria, Woodbury, N. assignor to Socony-Vacuum Qil Company, Incorporated, a corporation of New York No Drawing. Application September 28, 1944, Serial No. 556,287

Claims. i

This invention relates to mineral oil compositions and more particularly relates to viscous mineral oil fractions containing small amounts of an added material which imparts improved pour or flow characteristics thereto.

As is well known in the art, mineral oil fractions, such as those derived'from paraffin base crudes which have been refined for use as lubricants, normally contain an amount of waxsuch that,they congeal or become non-flowing at temperatures only slightly below normal temperatures. Obviously, oil fractions so characterized are impractical for general use. Although it is possible to remove an appreciable amount of this wax by additional refining operations and thereby materially reduce the pour point" of the oil, such refining operations are expensive and, in addition, seriously reduce the lubricant qualities of the oil. Apparently, the wax present in the oil solidifies in the form of a lattice-like structure and encloses the oil, thereby undesirably congealing the oil, yet contributing desirable lubricating qualities thereto. Accordingly, rather than resort to expensive refining operations to remove the wax and sacrifice some of the lubricating quality of the oil, it has become the practice to allow the wax to remain in the oil and to counteract its undesirable efiect upon the pour characteristics of the oil by incorporating therein a small amount of an agent capable of improving the said pour characteristics. Improving agents of this type are generally described as pour depressants in view of their ability to modify or retard wax crystallization so that impairment'of fiow does not take place except at temperatures well below those normally encountered in the use of the oil. The present invention has to do with an improving agent of this type which is greatly effective in very small quantities.

The present invention is predicated upon the discovery that a mineral oil fraction containing a small amount of an ester of lignin and of an aliphatic acid having at least about 16 carbon atoms is characterized by an appreciably lower pour point than is the mineral oil fraction alone. While all esters of the aforesaid class possess pour point depressant properties, those of certain subclasses are particularly effective in this regard. Lignin esters wherein at least 3 hydroxyl groups of the lignin are esterified with a saturated monocarboxylic aliphatic acid of the aforesaid type are outstanding and particularly so are those esters wherein the lignin is obtained from hardwood.

2 Representative of the aliphatic acids which form one component of the esters contemplated herein are palmitic, stearic, arachic, behenic, lignoceric, cerotlc, melissic, etc. Preferred of such acids, however, are palmitic and stearic.

With respect to the second component of the aforesaid esters, namely, lignin, it is recognized that the structure thereof is still in the controversial stage. Yet, many aspects of its nature are known and are such as to definitely establish its identity in the art. It is known that it occurs in plant life, such as shrubs, straw, trees, such as hardwoods, typified by oak, and softwoods typified by pine, etc.; and may be extracted therefrom by various means. For example, lignin may be extracted from plant life with cold concentrated acid, with hot caustic solutions, etc. It is also known that lignin differs from carbohydrates in its carbon and hydrogen content, analyses for lignin generally ranging from about 60 per cent to 65 per cent carbon and 5 per cent to 6 per cent ,carbon, with the remainder oxygen. It has also been. established that the methoxyl (-OCH3) content varies from about 14 per cent to about 21 per cent indicating the presence of 5 or 6 methoxyl groups per unit molecule. Analyses have also indicated that lignin is-characterized with 4 or 5 hydroxyl (-OH) groups. It has been suggested, for example, that lignin obtained .after dissolved in hot benzol.

from hardwoods has 6 methoxyl groups and 5 bydroxyl groups; whereas lignin obtained from softwoods, usually has 5 methoxyl and 5 hydroxyl groups. The molecular weight of lignin obtained from various plants has varied considerably, workers in this field reporting molecular weights from about 780 to about 1800. Strong acids have little or no effect upon lignin, as have most organic solvents. Lignin is illustrated hereinafter in the examples. "I

The preferred method of preparing the esters contemplated herein is that wherein lignin is dissolved -ln pyridine and is heated at an elevated temperature with an acid halide, followed by precipitation of the ester so formed upon the addition of water. The ester so. precipitated is then purified; it is washed with water and theretion so obtained is filtered, and the filtrate dis tilled to remove benzol therefrom. At this stage, the ester is relatively pure and may be used herein; however, it may be further purified whensdissolved in ether, then waished'withsodiumearbonate solution, dried with a drying agentsuch as calcium chloride and heated to evaporates'ether therefrom. 5 at The benzol solu- To facilitate handling, the esters may be prepared in an oil blend. For example, after lignin has been reacted with an acid halide, three parts by weight of mineral oil may be added to the reaction mixture and the purification procedure, described above, may then be followed. In this way, the final product is obtained as a 25 per cent blend in mineral oil, which is more convenient to work with than a more concentrated, or pure, product.

Illustrative of the lignin esters and of their methods of Preparation are those described in the examples provided below. The lignin used in the preparation of the esters described below is obtained from hardwood such as spruce chips according to the following procedure. A soda black liquor obtained by cooking spruce chips, that is hardwood chips, in an autoclave, under pressure, for several hours with a per cent sodium hydroxide solution was evaporated until the specific gravity was about 1 and the total solids about 20 per cent. Carbon dioxide was passed into the solution until the pH thereof was lowered to about 8.5, whereby a portion of the lignin separated out. The lignin so separated was coagulated by heating the same to about 100 C. and thereafter cooling it to about 50 C. It was then filtered, washed with water, and then washed with dilute mineral acid. It was finally washed with water and dried. The lignin so obtained had a molecular weight of about 850.

Examru: ONE

Preparation of lignin 'stearate Forty grams of lignin, described above, was dissolved in 30 grams of pyridine and 100 grams of dioxane, and warmed to about 50 C. Eighty grams of stearyl chloride was then added slowly, during a. thirty minute period, to the lignin dissolved in pyridine and dioxane. After all of the stearyl chloride had been added, the resulting mixture was heated to 100 C. and was maintained at the latter temperature for about 2 hours. Thereafter, the mixture was cooled and diluted with water whereupon the crude product, lignin stearate, precipitated out of the mixture. The crude product was washed with water and then dissolved in benzol. The benzol solution thus formed was filtered and the benzol was distilled from the filtrate to obtain substantially pure lignin stearate. Th product is a hard,

brown. wax-like solid.

ExAMPLn 'Iwo Preparation of lignin. palmztate Thirty-one grams of lignin, described above, were dissolved in 25 grams of pyridine and 100 grams of dioxane, and reacted with 50 grams of palmityl chloride as described in Example One above. The product, lignin palmitate, is also a hard, brown, wax-like solid.

The following data illustratethe pour point depressing action of the lignin esters contemplated herein upon mineral oils of the motor lubricant type. The oils used in these tests were: oil A, a Mid-Continent, solvent-refined, S. A. E. 30 grade oil having a Saybolt Universal viscosity of 65seconds at 210 F., and a pour point of +20" .13. .The results of pour tests upon oil blends of these oils and typical ligmn esters are provided in the table below.

Table Cone. on Lignin ester weight g per cent From the foregoing data, it will be apparent that lignin esters of the class contemplated herein depress the pour points of oils to which they are added to a substantial degree, although used therein in but minute quantities.

Not only are the aforesaid lignin esters of value as pour point depressants, but they are of value as wax modifiers for other purposes such as dewaxing aids in oil refining and the like. In general, they may be used in all cases wherein it is desired to modify the crystal structure of paraffin wax. They may be used in mineral oil fractions in concentrations of from about 0.05 per cent to about 10 per cent depending upon the character of the oil fractions and their conditions of use. Satisfactory results, however, are generally obtained with concentrations of the order of 005-02 per cent.

It is to be understood that while certain preferred procedures for synthesizing the improving agents contemplated herein and certain illustrative reactants which may be employed have been recited herein, the invention is not to be construed as limited thereto. Rather, the invention is to be broadly construed in the light of the language of the appended claims.

I claim:

1. A mineral oil composition comprising a viscous mineral oil fraction having in admixture therewith a minor proportion, sufflcient to depress the pour point of said oil fraction, of a lignin ester of an aliphatic acid having at least about 16 carbon atoms.

2. A mineral oil composition comprising a viscous mineral oil fraction having in admixture therewith a minor proportion, from about 0.05 percent to about 10 percent, of a lignin ester of an aliphatic acid having at least about 16 carbon atoms.

3. A mineral oil composition comprising a viscous mineral oil fraction having in admixture therewith a minor proportion, sufiicient to depress the pour point of said oil fraction, of a. lignin ester of a saturated mono-carboxylic aliphatic acid having at least about 16 carbon atoms.

4. A mineral oil composition comprising a viscous mineral oil fraction having in admixture therewith a minor proportion, suflicient to depress the pour point of said oil fraction, of an ester of lignin and of a saturated mono-carboxylic aliphatic acid having at least about 16 carbon atoms, at least 3 hydroxyl groups of the lignin being esterified with said acid.

5. A mineral oil composition comprising a viscous mineral oil fraction having in admixture therewith a minor proportion, suificient to depress the pour point of said oil fraction, of an ester of a hardwood lignin and of a saturated mono-carboxylic aliphatic acid having at least about 16 carbon atoms, at least 3 hydroxyl groups of the lignin being esterifled with the said acid.

6. A mineral oil composition comprising a viscous mineral oil fraction having in admixture therewith a minor proportion, sufiicient to depress the pour point of said 011 fraction, of an ester of a hardwood lignin having a molecular weight of about 850' and of a saturated monocarboxylic aliphatic acid having at least about 16 carbon atoms, at least 3 hydroxyl groups of the lignin being esterified with said acid.

'7. A mineral oil composition comprising a viscous mineral oil fraction having in admixture therewith a minor proportion, suflicient to depress the pour point of said oil fraction, of an ester of a hardwood lignin and of stearic acid, at-

least 3 hydroxyl groups of the lignin being esterifled with said acid.

8. A mineral oil composition comprising a viscous mineral oil fraction having in admixture therewith a minor proportion, suiiicient to de- 6 i press the pour point of said oil fraction, of a lignin stearate, said lignin having a molecular Weight of about 850 and having at least 3 hydroxyl groups esterified with said acid.

9. A mineral oil composition comprising a viscous mineral oil fraction having in admixture therewith a minor proportion, sufficient to depress the pour point of said oil fraction, of an ester of a hardwood lignin and of palmitic acid, at least 3 hydroiwl groups of the lignin being esterifled with said acid.

10. A mineral oil composition comprising a viscous mineral oil fraction having in admixture therewith a minor proportion, suflicient to depress the pour point of said oil fraction, of a lignin palmitate, said lignin having a molecular weight of about850 and having at least 3 hydroxyl groups esterified with said acid.

. JOHN J. GIAMMARIA. 

